In order to develop a practical facial image recognition technology, as it is also necessary to properly deal with a non-frontal face or a face whose expression changes, a normalization of a change in an appearance (pattern) of a face with respect to a posture or a transformation has been an important problem. Also, a specialized equipment such as a rangefinder or a stereo device, which directly measures a three-dimensional shape, not being preferable in terms of cost, it is desirable that a process can be started with only one image in order also to broaden an applicable scope.
JP-A-2007-4767 (Kokai) discloses a method of calculating a correspondence relationship between an input image and a three-dimensional model using a plurality of common feature points, to generate a normalized image from only one input image not only for a two-dimensional transformation such as a rotation or size within a screen, but also for a three-dimensional transformation such as a change in a facial posture, and to perform a recognition.
However, there is an influence due to individual differences when a facial image to be processed and the three-dimensional model are not identical. Also, in a case of including a partial transformation such as a smile in a face which is a processing object, as it cannot be expressed with a single three-dimensional model, there has been a possibility of an error occurring in the calculation of the correspondence relationship, and a recognition accuracy decreasing.
As heretofore described, in the conventional technology, there has been a problem that the correspondence relationship between the input image and the three-dimensional model cannot be effectively calculated due to an individual difference or a partial transformation of the face such as a change in facial expression.